Cables suitable for hauling and power and signal transmission are typically used for the installation, operation and retrieval of electrical submersible pumps used in oil wells. The conventional cable used for this purpose is generally round and comprises a core of the power and signal transmission lines surrounded by helically wound wires. There are, however, four significant disadvantages of these conventional cables.
First, under tension the helically wound wires experience significant inwardly directed forces that stress and can damage the internal core of the cable. Secondly, under compression, the helically wound wires tend to open up outwardly or inwardly, i.e. "birdcage", which distorts the strands of the wires and can inwardly compress and possibly damage the cable core. Thirdly, when such round cables contained by helically wound wires experience elevated temperatures and undergo outward expansion of the core, this again tends to generate destructive compressive stresses within the cable. Finally, these round cables cannot be winched directly onto a drum under high tension because they do not have the ability to carry out the resultant high sidewall bearing forces and therefore are easily crushed.
Other prior art cables having hauling and power and signal transmission lines are not easily bendable along the longitudinal axis and therefore are not easily stored on or deployed from a drum. Moreover, many of these cables are rather heavy and therefore do not have a high strength-to-weight ratio. They are also bulky, difficult to manufacture, and provide insufficient compression resistance.
Examples of these prior art cables are disclosed in the following U.S. Pat. Nos. 2,544,233 to Kennedy; 3,679,812 to Owens; 3,843,829 to Bridges et al; 4,081,602 to Paniri et al; 4,196,307 and 4,262,703 to Moore et al; 4,374,530 to Walling; 4,445,593 to Coleman et al; and 4,453,035 to Neuroth. In addition, an example of such prior art is disclosed in United Kingdom Pat. No. 1,250,823 to Spencer.